Orbital order and spin–orbit coupling in [formula omitted

Abstract

The correlated 3d sulphide BaVS 3 undergoes a sequence of three symmetry-breaking transitions which are reflected in the temperature dependence of the magnetic susceptibility, and its anisotropy. We introduce a microscopic model based on the coexistence of wide band a 1 g and localized e g d-electrons, and give the classification of the order parameters under the double space group and time reversal symmetries. Allowing for the relativistic spin–orbit coupling, the d-shell multipoles acquire a mixed spin–orbital character. It follows that orbital ordering is accompanied by a change in the susceptibility anisotropy.